A practical left ventricular assist pump is urgently needed to temporarily maintain the circulation of patients with profound left ventricular failure. This failure occasionally follows open heart surgery or may be a result of a major myocardial infarction. Evidence to date suggest that recovery of mechanical function of the left ventricle will occur in many instances, provided the circulation is adequately maintained in the interim. After evaluating a series of pump designs, our interdisciplinary group has developed a modified sac type pump (the angle port pump), which has been used as a paracorporeal left ventricular-to-aorta assist pump in a series of calves with both normal and seriously impaired left ventricular function. The pump has proven safe and effective for periods of continuous circulatory assistance of one to 2 months. The assist pump has now been employed in 4 patients. It has supported the circulation in three instances. One patient is alive and improving one month after pump removal. We propose to continue the development and evaluation of the assist pump over the next 5 years. Minor, but significant, improvements in pump design will be made. Each year, 12 calves with profound left ventricular failure will undergo one month of continuous assist pumping. The pump will then be removed and the calf sacrificed at a later date. Specific attention will be directed to: a) evaluation of left ventricle recovery, both in terms of pump function and muscle mechanics studies; b) right ventricle function studies; c) left ventricular myocardial oxygen consumption determinations; d) regional circulation before, during, and after left ventricular assistance; and e) coagulation and platelet function studies. Appropriate control studies will be performed. The development of the electrical energy convertor will continue and will include chronic calf studies in preparation for intermediate and long-term mechanical circulatory support with completely implanted devices. Use of the assist pump in properly selected patients is an important part of this proposal. In order to increase the patient use in this project from 4 times a year to 8 times, a collaborative arrangement with New York University Medical Center is proposed.